In Long Term Evolution (LTE) system, Orthogonal Frequency Division Multiplexing (OFDM) technology is used, take LTE-Time Division Duplexing (LTE-TDD) system for example, its frame structure is shown in FIG. 1. The basic resource unit that could be scheduled by the LTE system is Physical Resource Block (PRB), each PRB comprising 12*15 KHz bandwidth and 1 ms time slot unit (subframe). In time domain of system, each frame could be divide into two half-frame, each half-frame could be divide into five subframe. In frequency domain of system, different bandwidth could be divided into 50 PRB or 100 PRB etc.
Under co-frequency networking condition, neighboring cell interference is the main interference. It should use interference suppression and interference coordination technology to reduce co-frequency interference and improve the spectral efficiency of the system.
Multi-antenna forming technology could effectively inhibit neighboring cell co-frequency interference, Multi-antenna forming technology is to improve intensity of useful signal in user direction and to inhibit interference power in other direction according to space beam, thus to improve receiving signal-to-noise ratio of useful signal. However, this interference suppression is random, when the locations of neighboring cell users and home cell users, which are scheduled on the same frequency band, are close, it could cause strong interference.
Interference coordination technology is widely used in LTE system, it generally comprises static part frequency multiplexing technology and semi-static interference coordination technology.
Principle of the static part frequency multiplexing technology is shown as follow: each cell-edge user could only use part of the entire available frequency band, and frequency resources of neighboring cell-edges are mutually orthogonal, on each cell edge, available frequency band could be sent under high power to improve edge performance; in the cell interior, it could use entire frequency resources, in order to reduce the interference to neighboring cell, it should limit the maximum transmitting power when using the frequency band of neighboring cell edge.
Semi-static interference coordination technology semi-statically adjustments resource subset allocated to cell-edge users by interacting resource using information through X2 interface (communication interface between eNBs). Each cell gets resource using information by estimating resource requirement of cell-edge users of home cell and detecting interference of each frequency band and other ways, and interacts resource using information through X2 interface, to achieve coordination between cells, thus to reduce inter-cell interference.
In current method for interference coordination, the home cell users and neighboring cell users scheduled on the same subband is completely random, that would cause the follow problems:
1) Quality of user channel will vary with the location change of neighboring cell users scheduled on the same frequency band, so there could be a condition that channel interference is strong;
2) Quality of user channel will vary with the location change of neighboring cell users scheduled on the same frequency band, so when the system uses Adaptive Modulation and Coding (AMC) technology, it's difficult to accurately forecast channel quality, that increases the Block Error Rate (BLER).